Anomalous Resistivity Behavior Research Articles

Theoretical study on the origin of anomalous temperature-dependent electric resistivity of ferromagnetic semiconductor

Employing Korringa–Kohn–Rostoker Green’s function methodology, our investigation elucidates the previously obscure origins of the anomalous temperature-dependent electrical resistivity behavior of (Ga,Mn)As ferromagnetic semiconductors. Phonon and magnon excitations induced by temperature effects are addressed via the coherent potential approximation, while the Kubo–Greenwood formula is employed to compute transport properties. Consequently, the anomalous temperature-dependent electrical resistivity arising from the ferromagnetic–paramagnetic transition is successfully replicated. Our examination of electronic structures and magnetic interactions reveals pivotal roles played by antisite defects and interstitial Mn atoms in governing this behavior. As this approach enables both the estimation of temperature-dependent transport properties and the assessment of underlying mechanisms from a microscopic standpoint, it holds significant potential as a versatile tool across diverse fields.

Revealing the band structure of ZrTe5 using multicarrier transport

The layered material ZrTe$_5$ appears to exhibit several exotic behaviors which resulted in significant interest recently, although the exact properties are still highly debated. Among these we find a Dirac/Weyl semimetallic behavior, nontrivial spin textures revealed by low temperature transport, and a potential weak or strong topological phase. The anomalous behavior of resistivity has been recently elucidated as originating from band shifting in the electronic structure. Our work examines magnetotransport behavior in ZrTe$_5$ samples in the context of multicarrier transport. The results, in conjunction with ab-initio band structure calculations, indicate that many of the transport features of ZrTe$_5$ across the majority of the temperature range can be adequately explained by the semiclassical multicarrier transport model originating from a complex Fermi surface.

High conductivity and low activation energy in p-type AlGaN

Record-low p-type resistivities of 9.7 and 37 Ω cm were achieved in Al0.7Ga0.3N and Al0.8Ga0.2N films, respectively, grown on single-crystal AlN substrate by metalorganic chemical vapor deposition. A two-band conduction model was introduced to explain the anomalous thermal behavior of resistivity and the Hall coefficient. Relatively heavy Mg doping (5 × 1019 cm−3), in conjunction with compensation control, enabled the formation of an impurity band exhibiting a shallow activation energy of ∼30 meV for a wide temperature range. Valence band conduction associated with a large Mg ionization energy was dominant above 500 K. The apparently anomalous results deviating from the classical semiconductor physics were attributed to fundamentally different Hall scattering factors for impurity and valence band conduction. This work demonstrates the utility of impurity band conduction to achieve technologically relevant p-type conductivity in Al-rich AlGaN.

My research life about titanium and its alloys; from investigation about anomalous behavior of electrical resistivity to development of low cost beta type titanium alloys

My research life about titanium and its alloys; from investigation about anomalous behavior of electrical resistivity to development of low cost beta type titanium alloys

Structural Features, Anisotropic Thermal Expansion, and Thermoelectric Performance in Bulk Black Phosphorus Synthesized under High Pressure.

Black phosphorus (BP) allotrope has an orthorhombic crystal structure with a narrow bandgap of 0.35 eV. This material is promising for 2D technology since it can be exfoliated down to one single layer: the well-known phosphorene. In this work, bulk BP was synthesized under high-pressure conditions at high temperatures. A detailed structural investigation using neutron and synchrotron X-ray diffraction revealed the occurrence of anisotropic strain effects on the BP lattice; the combination of both sets of diffraction data allowed visualization of the lone electron pair 3s2. Temperature-dependent neutron diffraction data collected at low temperature showed that the a axis (zigzag) exhibits a quasi-temperature-independent thermal expansion in the temperature interval from 20 up to 150 K. These results may be a key to address the anomalous behavior in electrical resistivity near 150 K. Thermoelectric properties were also provided; low thermal conductivity from 14 down to 6 Wm-1K-1 in the range 323-673 K was recorded in our polycrystalline BP, which is below the reported values for single-crystals in literature.

Quantitatively determining the degree of spin fluctuations in actinide metals and compounds

Actinide materials are well-documented for nuclear properties, but their 5f electrons that produce exotic phenomena are not, due to the complexity of a dual localized and itinerant nature that remains a mystery. Particular interest is given to the electronic correlations at the localized and itinerant boundary where strong spin fluctuations are present. We report the identification of an intensity defined by integrating the normalized resistivity that approximately provides a quantitative measure of spin fluctuations. The intensity is very sensitive to the tuning of non-thermal parameters such as pressure and chemical doping, probing the anomalies in the evolution of spin fluctuations close to a valence or magnetic instability. In this way, our results are not only connected with the long-standing controversy on the anomalous low-temperature resistivity behavior of actinide metals, but also highlight an unconventional type of superconducting pairing, mediated by valence and/or spin fluctuations, for a wealth of 4f and 5f-electron systems. In an unified picture proposed, it is helpful to determine the degree of spin fluctuations for understanding the origin of the emergent superconductivity in systems with correlated electrons.

Ferroelectric Exchange Bias Affects Interfacial Electronic States.

In polar oxide interfaces phenomena such as superconductivity, magnetism, 1D conductivity, and quantum Hall states can emerge at the polar discontinuity. Combining controllable ferroelectricity at such interfaces can affect the superconducting properties and sheds light on the mutual effects between the polar oxide and the ferroelectric oxide. Here, the interface between the polar oxide LaAlO3 and the ferroelectric Ca-doped SrTiO3 is studied by means of electrical transport combined with local imaging of the current flow with the use of scanning a superconducting quantum interference device (SQUID). Anomalous behavior of the interface resistivity is observed at low temperatures. The scanning SQUID maps of the current flow suggest that this behavior originates from an intrinsic bias induced by the polar LaAlO3 layer. Such intrinsic bias combined with ferroelectricity can constrain the possible structural domain tiling near the interface. The use of this intrinsic bias is recommended as a method of controlling and tuning the initial state of ferroelectric materials by the design of the polar structure. The hysteretic dependence of the normal and the superconducting state properties on gate voltage can be utilized in multifaceted controllable memory devices.

Low temperature anomalies and room temperature magnetism in In0.95Fe0.05Sb dilute magnetic semiconducting film

We report the results of structural, electrical, surface morphological, and magnetic studies on the undoped and dilute Fe (0.05) doped InSb films (In0.95Fe0.05Sb) using the grazing angle X-ray diffraction technique, the quantum design physical property measurement system, atomic force microscopy (AFM), magnetic force microscopy (MFM), and the quantum design magnetic property measurement system. The In0.95Fe0.05Sb film of 500 nm thickness is grown on the silicon (Si) substrate using the thermal evaporation technique. A systematic investigation of electrical resistivity as a function of temperature and magnetic field is embarked. The electrical resistivity of the respective sample exhibits an upturn at approximately 15 K in the ferrimagnetic region. This theory explains the anomalous behavior of the electrical resistivity based on electron-electron, electron-phonon, electron-magnon, and Kondo-like spin-dependent scattering. The high-temperature data above 300 K are interpreted using the adiabatic small polaron hopping model. The AFM study shows the uniform particle size distribution, whereas the magnetic interaction at the surface is seen through MFM. The zero-field cooled magnetization measurement shows the transition at ∼65 K. The hysteresis curve at 10 K shows the ferrimagnetic behavior of the In0.95Fe0.05Sb film with coercivity and residual magnetization values of ∼100 Oe and 6.8811 emu, respectively.

Anomalous Electrical Conductivity and Magnetization in Fe–Cr–Ni Austenite–Martensite Alloys

We have measured the temperature dependence of the resistivity and magnetization of a special steel of the Fe–Cr–Ni austenite–martensite class in a wide temperature range (77–1100 K). It is found that at temperatures 77–170 K, the resistivity of the material almost remains unchanged, but upon a further increase in temperature, the resistivity sharply increases, which is probably a result of disordering. In addition, anomalous behavior of resistivity with vanishing spontaneous magnetization is observed at 910 K, which is associated with the ferromagnet–paramagnet phase transition. Comparison of the measured ρ(T) dependence with the analogous dependence for 12Kh18N10T austenite stainless steel has not revealed features typical of Fe–Cr–Ni steel.

Аномальная электропроводность и намагниченность в сплавах системы Fe-Cr-Ni аустенитно-мартенситного класса

AbstractWe have measured the temperature dependence of the resistivity and magnetization of a special steel of the Fe–Cr–Ni austenite–martensite class in a wide temperature range (77–1100 K). It is found that at temperatures 77–170 K, the resistivity of the material almost remains unchanged, but upon a further increase in temperature, the resistivity sharply increases, which is probably a result of disordering. In addition, anomalous behavior of resistivity with vanishing spontaneous magnetization is observed at 910 K, which is associated with the ferromagnet–paramagnet phase transition. Comparison of the measured ρ( T ) dependence with the analogous dependence for 12Kh18N10T austenite stainless steel has not revealed features typical of Fe–Cr–Ni steel.

Features of magnetoresistance and magnetic properties in Bi95.69Mn3.69Fe0.62

A study of textured, polycrystalline Bi95.69Mn3.69Fe0.62 containing two phases: the bismuth matrix and inclusions of the α-BiMn phase. It is shown that the anomalous behavior of the magnetization temperature dependences can be linked to the reorientation transition of the Mn magnetic moments in the α-BiMn phase, caused by the change in the sign of the magnetic anisotropy constant. It is established that the temperature dependences of the electrical resistivity in a magnetic field are non-monotonic, and that the magnetoresistance is positive in all temperature ranges, reaching a maximum value of 3033% for a magnetic field of 140 kOe, when the magnetic field is perpendicular to the transport current. A strong anisotropy of electrical resistivity is measured in a magnetic field. It is assumed that the anomalous behavior of the electrical resistivity as a function of temperature in Bi95.69Mn3.69Fe0.62, as compared to pure bismuth, is linked to a change in the overlap between the electron and the hole Fermi surfaces under the influence of α-BiMn phase magnetism, as well as the magnitude and direction of the external magnetic field.

Observation of Anomalous Resistance Behavior in Bilayer Graphene

Our measurement results have shown that bilayer graphene exhibits an unexpected sharp transition of the resistance value in the temperature region 200~250 K. We argue that this behavior originates from the interlayer ripple scattering effect between the top and bottom ripple graphene layer. The inter-scattering can mimic the Coulomb scattering but is strongly dependent on temperature. The observed behavior is consistent with the theoretical prediction that charged impurities are the dominant scatters in bilayer graphene. The resistance increase with increasing perpendicular magnetic field strongly supports the postulate that magnetic field induces an excitonic gap in bilayer graphene. Our results reveal that the relative change of resistance induced by magnetic field in the bilayer graphene shows an anomalous thermally activated property.

Liquid–liquid phase equilibrium in ternary immiscible Al–Bi–Sn melts

ABSTRACTIn this paper, the liquid-phase separation of ternary immiscible Al–Bi–Sn melts was studied with resistivity and thermal analysis methods at different temperatures. The resistivity–temperature curves appear anomalous and abrupt change as rising temperature, corresponding to the distinctive and low peak of melting process in the differential scanning calorimetry (DSC) curves, indicative of the occurrence of the liquid-phase separation. The anomalous behaviour of the resistivity temperature dependence is attributable to concentration–concentration fluctuations. The microheterogeneity–microhomogeneity transformation causes large fluctuations in concentration, which make the randomness and chaos of the atoms larger, leading to the greater impediment to electron movement and the sharp rise of resistivity. The addition of tin to the Al–Bi immiscible alloys decreases the monotectic reaction. It is concluded that concentration–concentration fluctuations are responsible for the anomalous behaviour of resistivity and DSC methods.

Topological Properties and the Dynamical Crossover from Mixed-Valence to Kondo-Lattice Behavior in the Golden Phase of SmS

We have investigated temperature-dependent behaviors of electronic structure and resistivity in a mixed-valent golden phase of SmS, based on the dynamical mean-field-theory band-structure calculations. Upon cooling, the coherent Sm 4f bands are formed to produce the hybridization-induced pseudogap near the Fermi level, and accordingly the topology of the Fermi surface is changed to exhibit a Lifshitz-like transition. The surface states emerging in the bulk gap region are found to be not topologically protected states but just typical Rashba spin-polarized states, indicating that SmS is not a topological Kondo semimetal. From the analysis of anomalous resistivity behavior in SmS, we have identified universal energy scales, which characterize the Kondo-mixed-valent semimetallic systems.

Ga Substitution and Oxygen Diffusion Kinetics in Ca3Co4O9+δ-Based Thermoelectric Oxides

The influence of Ga doping on the crystal structure and cobalt oxidation state of Ca3Co4O9+δ was determined using synchrotron X-ray diffraction and X-ray absorption near-edge spectroscopy. The results show that Ga is preferentially located on the Co site in the rock-salt-type [Ca2CoO3] layer, up to a maximum occupancy of ∼2.2%, and that doping does not change the cobalt oxidation state of this material. We find that the doping-induced point defect scattering and modification of charge carrier concentration result in lower thermal conductivity and lower electrical resistivity, thereby improving the thermoelectric figure of merit in the Ga-doped Ca3Co4O9+δ material. In addition, the influence of sample density and measuring atmosphere on their thermoelectric performance was found to be significant. It is believed that the interconnected pore structure in the low-density sample facilitates oxygen out-diffusion from the lattice, which leads to anomalous electrical resistivity behavior at elevated temperatures...

Anomalous Resistivity and the Electron–Polaron Effect in the Two-Band Hubbard Model with One Narrow Band

We search for anomalous normal and superconductive behavior in the two-band Hubbard model with one narrow band. We analyze the influence of the electron–polaron effect and the Altshuler–Aronov effect on effective mass enhancement and scattering times of heavy and light components in the clean case. We find anomalous behavior of resistivity at high temperatures $T > W_{h}^{*}$ both in 3D and 2D situations. The SC instability in the model is governed by an enhanced Kohn–Luttinger effect for p-wave pairing of heavy electrons via polarization of light electrons.

Enhanced survival of short-range magnetic correlations and frustrated interactions in [formula omitted] intermetallics

Elastic and inelastic neutron scattering and magnetization measurements have been used to study peculiarities of the magnetic state in R3T compounds (R=Gd, Er, Tb; T=Ni, Co) below and above magnetic ordering temperatures. A pronounced non-Brillouin shape of the magnetization curves observed in the antiferromagnetic compounds Gd3Ni and Tb3Ni above their magnetic ordering temperatures together with earlier reported data about the retention of the magnetic contribution to the total specific heat of Gd3T and anomalous behavior of the electrical resistivity above magnetic ordering temperatures are ascribed to the existence of short-range magnetic correlations in the wide temperature range in the paramagnetic state. The persistence of short-range magnetic order up to temperatures greater than 5–6 times the Néel temperature has been revealed by powder neutron diffraction measurements performed for Tb3Ni and Tb3Co. On the other hand, results from inelastic neutron scattering show that the low temperature magnetic excitations are strongly suppressed in both Tb3Co and Er3Co. It is suggested that the extended short-range magnetic correlations, which turn out to be an inherent feature of R3T type compounds, are due to the layered crystal structure and to the difference between geometrically frustrated intra-layer exchange interactions and inter-layer exchange.

Anomalous behavior of linear resistivity in the vanishing process along the intergrain ordering of weak-sintered ceramic superconductor YBa2Cu4O8

Intergrain ordering nature of weak-sintered ceramic of YBa2Cu4O8 (Y124) is studied experimentally by ultra precise electric resistivity observation together with magnetic measurements for linear and nonlinear susceptibilities. For this purpose, a new method to detect pure linear resistivity down to the order of 1 nΩm has been developed with the help of combination technique of pulse delta method and FFT treatment. Making use of this experimental system for several weak-sintered Y124 samples, it has been revealed that linear resistivity first drops toward zero steeply with decreasing temperature, and then turns abruptly upward to forms faint maximum at lower temperature. Such peaking of electric resistivity has been found to occur below the intergrain ordering temperature that was estimated by the magnetic behavior. This newfound phenomenon, to say 'revival of resistivity', is being regarded as general nature for the weak-sintered ceramics, and considered to be an intrinsic frustration effect for actual d-wave type ceramics of irregular network structure.

Observation of Oscillatory Resistance Behavior in Coupled Bernal and Rhombohedral Stacking Graphene

We report on the first observation of an anomalous temperature-dependent resistance behavior in coupled Bernal and rhombohedral stacking graphene. At low-temperature regime (<50 K) the temperature-dependent resistance exhibits a drop while at high-temperature regions (>250 K), the resistance increases. In the transition region (50-250 K) an oscillatory resistance behavior was observed. This property is not present in any layered graphene structures other than five-layer. We propose that the temperature-dependent resistance behavior is governed by the interplay of the Coulomb and short-range scatterings. The origin of the oscillatory resistance behavior is the ABCAB and ABABA stacking configurations, which induces tunable bandgap in the five-layer graphene. The obtained results also indicate that a perpendicular magnetic field opens an excitonic gap because of the Coulomb interaction-driven electronic instabilities, and the bandgap of the five-layer graphene is thermally activated. Potentially, the observed phenomenon provides important transport information to the design of few-layer graphene transistors that can be manipulated by a magnetic field.

Anomalous behavior of linear resistivity arising in intergrain ordering process of weak-sintered ceramic system YBa2Cu4O8

Faint electric resistivity behavior is searched experimentally near and below intergrain ordering temperature of weakly sintered ceramic YBa2Cu4O8 (Y124). For this purpose, a new method to detect linear and nonlinear resistivity sensitively by combination of pulse delta method and numerical Fourier-transformation has been designed. Making use of the experimental system for several weak sintered Y124 samples, it is revealed that linear resistivity just above the intergrain ordering point first drops toward zero steeply with decreasing temperature, and then turns abruptly upward to forms faint maximum at lower temperature. Such a novel behavior of ‘revival of resistivity’ is confirmed to be reproducible, and considered to be an essential frustration effect for d-wave type grain system with irregular or inhomogeneous ceramic structure.